Thermal Stability

HAYNES® 188 alloy is similar to the solid-solution-strengthened superalloys, such
as alloy 625 or HASTELLOY® X alloy, which will precipitate deleterious phases upon such long-ter m exposure. In this case. the phase in question is a CO2W laves phase. which serves to impair both tensile ductility and impact strength. The behavior of 188 alloy is significantly better in this regard than HAYNES® 25 alloy, which it replaced; but for applications where thermal stability is important, 230® alloy is recommended.

Room-Temperature Properties of Plate after Thermal Exposure

Exposure Temperature

-

0.2% Yield Strength

Ultimate Tensile Strength

Elongation

Impact Strength

°F

°C

h

ksi

MPa

ksi

MPa

%

ft.- lbs.

J

1200

650

0

65.0

450

140.0

965

56.0

143

194

8000

79.7

550

151.6

1045

29.1

23

31

1400

760

0

65.0

450

140.0

965

56.0

143

194

8000

74.0

510

147.9

1020

10.8

3

4

1600

870

0*

70.1

485

146.0

1005

50.4

143

194

1000

70.7

490

157.5

1085

28.7

10

13

4000

68.8

475

156.0

1075

26.6

10

13

8000*

64.5

445

147.4

1015

22.2

9

12

16000

63.8

440

146.1

1005

24.0

8

11

*Average of two test exposure. All other single exposures.

Comparative Impact Strength after 8000-Hour Exposures

Alloy

Solution-Annealed Charpy
V-Notch Impact

Charpy V-Notch Impact Following Exposure
For 8000 Hours at Temperatures